HTTP Nukesploit/Crime Pack activity 1

I noticed that Norton blocked two intrusion attempts by HTTP Nukesploit and Crime Pack activity 1 at the same time earlier tonight. The attacking computer was my own.

I've read through a few forums and I'm a little confused. A number of people seem to have had very similar experiences, but the responses vary from a diagnosis of a serious infection (followed by a horrendous series of scans and reports), to a reassurance that Norton has blocked a random attack - don't worry about it.

 

I've noticed that intrusion attempts are not uncommon, but the fact that these purport to be from my machine is rather unsettling.

 

Should I be worried?